It is known to provide a spindle press with a continuously driven and unidirectionally rotating flywheel which can be coupled to the spindle by a fluid-pressure-operated clutch so that the ram or tool of the press is urged against a workpiece. Upon decoupling of the flywheel from the spindle, the ram can, also via appropriate fluid-operated means, be withdrawn back into its starting position.
To establish the point at which the clutch is decoupled or disengaged, it is known to provide a valve which operates by inertia, i.e. continues to move when a rotating element is brought to standstill at the end of the press stroke. This continued movement is transformed into the opening of a valve to interrupt the energization of the clutch and decouple the flywheel from the spindle.
While some earlier spindle presses utilized pneumatic fluid operators, a hydraulic system is described in the German Open Application DE-OS 31 02 665 which utilizes an inertial valve operator in the manner described. In that system the inertial valve operator is a control mass which is provided at the head of the spindle and has freedom of rotating movement about the axis of rotation of the spindle.
This control mass is not, however, readily accessible and, while the spindle press in which it is used represents a significant advance over the art described in that application, the ability to compensate for varying desired operating conditions and workpiece deformations is not any easier than was the case with still earlier systems.
Consequently, although the earlier press of these applications is highly advantageous in many respects, it is capable of further improvement, particularly with respect to the ability of modify press operations to suit various conditions which may arise. One of the most important points at which improvement is desirable is in the elimination of the effect of elastic deformation in the spindle-to-spindle nut drive upon the termination of the clutch actuation, a phenomenon which is especially pronounced when comparatively slender spindles are provided.